Programmable carrier plate for automated circuit board tester

ABSTRACT

An apparatus and method for supporting and aligning a circuit board, such as a computer system board and the like, during testing. The apparatus includes a carrier plate having a plurality of holes arrayed in a grid. The holes are used for coupling various alignment components to the carrier plate. These alignment components include fixed tooling pins, adjustable tooling pins, and alignment blocks. In one embodiment, a template is employed to align the alignment components based on a form factor of the circuit board to be tested, wherein different templates are employed for circuit board-types having different form factors. The circuit board is supported by a plurality of plastic threaded fasteners to form a gap between the circuit board and the carrier plate. The templates are also used to locate these plastic supports. The carrier plate further includes a pair of alignment bushings for aligning the carrier plate relative to a test apparatus in which the carrier plate is to be employed.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application contains subject matter related to U.S.application Ser. No. 10/261,055, entitled “UNIVERSAL AUTOMATED CIRCUITBOARD TESTER,” and U.S. application Ser. No. 10/261,118, entitled“USB-CONTROLLABLE POWER SUPPLY,” both filed Sep. 30, 2002.

FIELD OF THE INVENTION

The field of invention relates generally to testing computer systemcircuit boards and, more specifically but not exclusively relates to aprogrammable carrier plate apparatus for employment in automatedcomputer system circuit board test equipment.

BACKGROUND INFORMATION

It is a common practice to perform testing of circuit boards, such ascomputer system boards (e.g., motherboards and the like) prior to theirsale or use in a computer system product. For example, as computersystem boards have evolved, an ever-increasing level of functionalityhas been built into the boards, such as integrated video subsystems,audio systems, network interfaces, modem circuitry, and the like.Testing to verify the integrity of such functionality is often performedduring quality control operations, either on an individual board basis,or using a random sampling scheme.

Generally, computer system boards are tested in the following manner.The board is mounted or otherwise coupled to a test plate or the like,and a plurality of input connectors are manually mated withcorresponding system board connectors to provide input power signals tothe system board and to coupled input/output (I/O) ports and the like toelectronic test equipment that is used to test the performance of thesystem board via a variety of test operations. Additional manualoperations typically include insertion of memory and/or microprocessors.This is a very laborious process, and is also very time-consuming. As aresult, the test throughput is low, and test costs are excessive.

In addition, when different types of computer system boards are to betested, the test environment will often require a uniquely-configuredtest station for each type of board. For example, different system boardtypes may require different power supply inputs, and/or may havedifferent memory slot locations. Accordingly, the test station used toperform testing of such system boards must be configured to accommodateany unique characteristics of the system boards. This adds to theexpense and complexity of a test environment. Furthermore, when thecomputer system board for a particular test station is phased-out ofproduction, the test station is often scrapped, as it cannot be used totest other types of system boards.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing aspects and many of the attendant advantages of thisinvention will become more readily appreciated as the same becomesbetter understood by reference to the following detailed description,when taken in conjunction with the accompanying drawings, wherein likereference numerals refer to like parts throughout the various viewsunless otherwise specified:

FIGS. 1A and 1B are isometric views of an automated universal circuitboard tester in accordance with one embodiment of the invention;

FIGS. 2A, 2B, and 2C respectively show exploded, frontal, and sideisometric views of the automated probe/connector insertion mechanismemployed an embodiment of the invention;

FIGS. 3A, 3B, and 3C respectively show fully disengaged, middle, andfully engaged actuation states corresponding to an actuation cycle ofthe automated probe/connector insertion mechanism;

FIG. 4 is an isometric view of a Side Access Unit (SAU);

FIG. 5 shows an isometric view of a programmable circuit board carrierplate;

FIGS. 6A and 6B respectively show exploded and assembled isometric viewscorresponding to a first exemplary configuration of a carrier plate;

FIGS. 7A and 7B respectively show exploded and assembled isometric viewscorresponding to a second exemplary configuration of a carrier plate;and

FIG. 8 is a plan view of a template used to assist in programming acarrier plate.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Embodiments of apparatus and methods for supporting and locating circuitboards in conjunction with performing automated testing of circuitboards, such as computer system boards and the like, are describedherein. In the following description, numerous specific details are setforth to provide a thorough understanding of embodiments of theinvention. One skilled in the relevant art will recognize, however, thatthe invention can be practiced without one or more of the specificdetails, or with other methods, components, materials, etc. In otherinstances, well-known structures, materials, or operations are not shownor described in detail to avoid obscuring aspects of the invention.

Reference throughout this specification to “one embodiment” or “anembodiment” means that a particular feature, structure, orcharacteristic described in connection with the embodiment is includedin at least one embodiment of the present invention. Thus, theappearances of the phrases “in one embodiment” or “in an embodiment” invarious places throughout this specification are not necessarily allreferring to the same embodiment. Furthermore, the particular features,structures, or characteristics may be combined in any suitable manner inone or more embodiments.

An overview of an embodiment of an automatic circuit board tester 100corresponding to a Scalable Universal Integrated Test System (SUITS) inwhich various embodiments of the invention described herein may beemployed is shown in FIGS. 1A and 1B. Automated circuit board tester 100includes a frame 102 to which a monitor 104 is attached via a boom 106.An automated connector insertion/probe mechanism 108 is housed withinthe frame, along with test electronics 110. The automated connectorinsertion/probe mechanism employs a carrier assembly 112 including acarrier plate 114 to which a circuit board comprising a device undertest (DUT) 116 (not shown) is coupled during testing. The mechanismfurther includes a universal cassette 118 to which a replaceable topprobe/connector plate 120 is attached, and a replaceable side accessunit (SAU) 122 that is used to connect to various I/O port connectorsgenerally disposed at the rear of the DUT. Additional SAU's may also beemployed for DUT's that include I/O ports on one or both sides of theDUT.

The test electronics for the SUITS tester include various circuit boardsthat are configured to support a universal test environment via a common(Universal Serial Bus (USB)) communication interface, whereby circuitboards having different configurations may be tested using a common(i.e., universal) tester. This is facilitated, in part, by a universalpower supply (UPS) 124 that receives power from a power distributionunit (PDU) 126 and supplies power to DUT 116 and other test electronicscomponents. The test electronics further include a digital videomeasurement unit (DVMU) 127 and combo board 128 used for audio,analog/digital video and USB 2.0 testing contained within a housingmounted to universal cassette 118.

In general, test operations are controlled by a host computer 130,disposed toward the bottom of the frame, which is linked incommunication with the test electronics via USB and serial communicationlinks. More specifically, the host computer is used to execute softwarecomprising a universal host controller (UHC) that is used to controltesting of the DUT. The system also includes a control panel 132 toenable user interaction, and provides an access door 134 to allow theDUT to be loaded and to prevent access to the DUT (and associated testelectronics) during testing. Furthermore, the tester includes removableside and top panels 136 and 138 that are installed during testingoperations so as to prevent access to the DUT and tester electronics, asshown in FIG. 1B. Further details of the tester electronics and softwareoperations performed during DUT testing are described in the relatedapplications identified above in the cross-reference to relatedapplication section.

Further details of automated connector insertion/probe mechanism 108 areshown in FIGS. 2A-C, and 3A-C. In one embodiment, a single linearactuator is employed to cause concurrent actuation about four orthogonalaxes. In one embodiment the linear actuator comprises a pneumaticcylinder 200, which has a body coupled a carriage 202 and a rodoperatively coupled to frame 102. The concurrent multi-axis actuationincludes a vertical actuation that is used to vertically move the DUT sothat it engages various connectors and probes disposed on the undersideof top probe/connector plate 120. This is enabled, in part, by means offour vertical actuation guide ramps 204, which are mounted on carriage202. Carriage 202 rolls on a plurality of wheels 206 mounted within aframe 208 that is mounted to frame members 210.

A vertical push plate 211 is provided to push carrier assembly 112upward. Four brackets 212 are coupled to the underside of vertical pushplate 211. A respective cam follower 213 is coupled towards the bottomof each of brackets 212 and is sized to fit within a corresponding slot214 formed in vertical actuation guide ramps 204.

Carrier assembly 112 includes a carrier frame 216 to which a pair oflinear bearings 218 are coupled. Likewise, a pair of similar linearbearings 219 are coupled to vertical push plate 211. Each of linearbearings 216 and 217 slidingly engage a mating vertically-disposedlinear bearing shaft 220 that is operatively coupled at its respectiveupper and lower ends to frame 102.

A drawer slide 222 is coupled between carrier frame 216 and a carrierplate support 224 on which carrier plate 114 rests to enable the carrierplate to be pulled forward relative to the carrier frame, therebyenabling a DUT that has just completed testing to be removed and a newDUT to be installed on the carrier plate. A knob 226 is provided tofurther assist an operator in pulling and pushing carrier plate 114.

In addition to a vertical actuation axis, three horizontal actuationaxes are also provided. These actuation axes correspond to respectiveside activation unit (SAU) actuators, which are used to actuate SAUs 122(removed for clarity in FIGS. 2A-2C). Each SAU actuator comprises a SAUcarriage 228 that is enabled to move linearly relative to carrier frame216 by means of end linear bearing assemblies 230 and a center linearbearing assembly 232. Each SAU carriage further includes a pair of camfollowers 234 that engage respective SAU actuation ramps 236 during SAUactuation.

Further details of universal cassette 118 and top probe/connector plate120 are shown in FIGS. 2B and 3A. The combination of universal cassette118 and top probe/connector plate 120 are designed to enabling testingof various DUT board types, wherein the functions provided by universalcassette 118 are “universal” to all board types, while topprobe/connector plate 120 is configured for a certain board type or setof board types. Accordingly, mounting provisions are provided to enabletop probe/connector plate 120 to be swapped out. These include a set oftoggle clamps 238 and plate alignment means that are used to align thetop probe/connector plate relative to the universal cassette.

Universal cassette includes various components that are used to simulatethe DUT functioning within an actual work environment, such as within acomputer. These include a floppy drive 240, a CD-ROM drive 242, and ahard disk drive (disposed beneath the floppy drive). Generally, theinterfaces to each of these devices are provided via connectors coupledon the underside of top probe/connector plate 120. Optionally, suchconnectors may be disposed on the underside of the universal cassettewhen the DUT types share a common configuration for such connectors.

Typically, different board types will have different connector/componentlayout configurations. Accordingly, each top probe/connector plate 120will be configured for a corresponding board type or set of types. Thismeans that the various probes 244 and connectors 246 will be configured,both in orientation and type, so as to mate with corresponding targetpads/traces/components and connectors for the DUT type. In addition togeneral connector types, such as power, and peripheral device (e.g.,disk drives, IDE, etc.) connectors, one or both of the topprobe/connector plate and universal cassette may employ peripheral(expansion) bus extenders 248, which enable various types of peripheralboards, such as video boards, sound boards, network interface cards(NICs), SCSI cards, special purpose cards, etc., to be operativelycoupled to the DUT during testing operations.

Another aspect of the automated insertion capabilities of the system isthe ability to automatically insert memory and/or microprocessors. Forexample, the top probe/connector plate may be configured to hold one ormore DIMMs (dual inline memory modules) 249, which are inserted intocorresponding DIMM connectors on the DUT. Additionally, if the DUT typeemploys a removable processor, such as a slot 1 processor, acorresponding processor may be mounted to the top probe/connector plateand inserted into a corresponding connector on the DUT.

Further details illustrating an actuator motion cycle are shown in FIGS.2A-C and 3A-C. FIGS. 2A and 3A show an initial configurationcorresponding to a fully-disengaged actuation condition. Under thiscondition, the pneumatic cylinder is fully retracted such that camfollowers 213 are at the bottom of vertical actuation guides 204. Whilein this position a lower position switch 250 will be engaged, which willenable access door 134 to be opened, thereby enabling an operator toinstall or remove a DUT. After the access door has been shut, theactuator sequence may begin. The position of the access door is sensedby a door engagement sensor 252.

A mid actuation position is shown in FIGS. 2B and 3B. In this instance,a valve is positioned to enable air to flow into pneumatic cylinder 200,causing the cylinder's rod to be extended. This cause carriage 202 tomove toward the left, which pushes vertical push plate 211 upward bymeans of engagement of cam followers 213 with vertical actuation guideramps 204. As is further shown, SAU cam followers 234 are about toengage SAU actuation ramps 236. Furthermore, carrier plate 114 ispositioned such that it is just below a pair of alignment posts 254.

A fully-engaged position is shown in FIGS. 2C and 3C. As vertical pushplate 211 is pushed upward, it engages carrier frame 216, which in turnsupports carrier plate 114, pushing the carrier plate upward in turn. Asthe carrier plate moves upwards, a pair of bushings 256 disposed in theplate begin to engage alignment post 254. Since the carrier plate is“floating” on carrier plate frame 224, the carrier plate is enabled toself align to the alignment posts. As the carrier plate is lifted inproper alignment via the alignment posts, various connectors 246 areengaged with corresponding connectors on the DUT, as well as variousprobes engaging with target traces, pads, components etc. At the sametime, memory DIMMs, a CPU, and peripheral expansion bus connectors arealso coupled, dependent on the particular DUT type configuration. Thiscompletes the vertical part of the automated test probe/connectorinsertion. Once the carriage assembly is at the top of the actuationcycle, testing operations may begin. This condition is indicated by afully-engaged (ACTUATOR_FULL_UP) position sensor 260.

In concurrence with the foregoing vertical actuation, horizontalactuation of the SAUs is performed. As the carriage assembly movesupward, SAU cam followers 234 engage SAU actuation ramps 236, causingSAU carriages 228 to be moved horizontally inward. As a result, theconnectors on the SAU (shown in Figure X) become engaged withcorresponding connectors on the DUT. For example, a typical DUT maycomprise an ATX-compatible motherboard, which includes a plurality ofconnectors having a predefined configuration that are mounted to themotherboard such that they can be horizontally accessed from opening inthe case in which the motherboard is to be installed. These connectorstypically include serial and parallel ports, as well as a keyboard port,a mouse port, and optional USB, game/audio ports, and network ports.Other types of ports may be provided as well.

An exemplary SAU 400 is shown in FIG. 4. SAU 400 includes a frame 401comprising a front plate 402 and a back plate 404, which are coupledtogether by means of a plurality of fasters 406 and standoffs 408. Apair of through holes 400 are drilled through each of the front and backplates to enable the frame to be coupled to a SAU actuator 228 via bolts264 (See, e.g., FIG. 2A). The SAU frame is used to hold a plurality ofconnectors coupled to front plate 402, including a keyboard portconnector 412, a mouse port connector 414, a first pair of USBconnectors 416, 418, and an IEEE 1394 connector 420. The connectorsfurther include a 9-pin SubD serial port connector 422 and a 25-pin SubDparallel port connector 424. An RCA audio connector 426 is disposedbeneath the parallel port connector, along with a fiber optic connector428. A set of audio jacks 430 are disposed to the left of the parallelport connector, along with provisions for a pair of additional audiojacks 432 to support future five-way audio interfaces. A second pair ofUSB connectors 436, 438 are disposed toward the left end of the frontplate, along with a conventional network RJ-45 connector 440.

Generally, the various connectors and jacks are arranged in a mannercorresponding to a standard configuration, such as the ATX standard. Itis not required that all of the connector and jacks be used, and in factdifferent SAUs may be employed for different DUT type configurations.

Each of the various SAU connectors and jacks is connected to a cablethat is used to carry signals to corresponding test electronics employedby the tester (not shown in FIG. 4). These include a keyboard cable 442,a mouse port cable 444, an IEEE 1392 cable 446, a serial cable 448, aparallel cable 450, and a network cable 452. Each of these cablesinclude an appropriate mating connector, as would be commonly employedin computer systems and the like. In the illustrated embodiment, wires454 connected to the various audio jacks are commonly coupled to aconnector 456.

In one embodiment, one or more of the connectors/jacks are springloaded, such as depicted by springs 458 and 460 in the illustratedembodiment. The springs enable different forces to be applied toindividual connectors and jacks when the SAU is urged forward to couplecorresponding connectors/pins on the DUT, and maintain a constant forceon connectors/jacks during the testing operations.

In some instances, only one of the three SAU axes may be employed, suchan axis that enabled connectors to be inserted at the back of the DUTvia a corresponding SAU. Under such situations, either or both of theside SAU actuators may be removed.

Reconfigurable “Programmable” Carrier Plate

With further reference to FIG. 5, carrier plate 114 provides a universalcircuit board mounting platform that may be adapted (programmed) tosecure DUTs having a variety of different form factors. The carrierplate includes a grid of threaded holes 500. The threaded holes enablevarious alignment blocks 502 to be positioned anywhere within the gridarea via corresponding threaded fasteners 504. They also enable supports506 to be located so as to support the DUT at desired locations. Ingeneral, the supports will be threaded, although this isn't required.Typically, supports 506 may comprise plastic fasteners to electricallyisolate the DUT from the carrier plate. In one embodiment, supports 506comprise nylon cap screws.

Preferably, threaded holes 500 will be arranged in an accurate grid. Inone embodiment ¼-20 threaded holes are arrayed in a 0.500 inch gridpattern. This enables accurate alignment of DUTs to the carrier plate(and thus indirectly to top probe/connector plate 120). In someimplementations, sufficient alignment may be facilitated by alignmentblocks 502 alone. In other instances, alignment may be facilitated byusing more accurate alignment means, such as alignment pins. Ininstances in which alignment holes formed in the DUT's circuit board (orin components attached thereto) have a spacing that coincides with amultiple of the grid pattern spacing, a pair of “fixed” tooling pins 508may be employed to align the DUT relative to the carrier plate. Ininstances in which the spacings do not coincide, a fixed tooling pin 508will be used at one end, while an adjustable tooling pin 509 will beused at the other end. In one embodiment, the adjustable tooling pinincludes a tooling pin 510 mounted on the end of a slotted bar 511, andis secured to the top of the carrier plate by means of shoulder screws512 and washers 514.

As discussed above, a pair of alignment bushings 256 are disposed withinholes 516 formed toward the front corners of carrier plate 114. In oneembodiment, the alignment bushings may be secured via a light press fit.In another embodiment, a “C” ring 518 is coupled toward a groove 520formed in the base of alignment bushing 256, whereby the alignmentbushing is secured via engagement with a shoulder 522 on the top side ofthe carrier plate and the C ring on the bottom side of the carrierplate.

Exemplary carrier plate configurations for mounting respective DUT's 600and 700 are shown in FIGS. 6A-6B and 7A-7B. Generally, a plurality ofalignment blocks 502 will attached to the carrier plate and configuredto surround the DUT on three or four sides (it is recommended that twosides be used as a minimum). This will typically provide a grossalignment of the DUT. As the DUT is lowered onto the carrier plate, theupper portion of the tooling pins is received by a correspondingalignment hole formed in the circuit board (as shown by alignment holes702 in DUT 700) or in a component mounted to the circuit board (notshown). Upon installation, the bottom of the DUT circuit board will besupported by the heads of supports 506.

To assist in reprogramming the carrier plate configuration, templatesmay be employed, such as template 800 shown in FIG. 8. Typically, eachtemplate will be made of a thin material such as plastic or metal, andinclude a means for locating and/or securing the template to the top ofthe carrier plate. For example, in one embodiment the template may belocated and secured via a plurality of alignment holes 802.

Each template will typically include a plurality of holes, slots, andcutouts arranged in a configuration corresponding to a particular formfactor for the DUT to which that templates corresponds. These includesupport holes 804, alignment block cutouts 806 and 808, fixed toolingpin holes 810, and adjustable tooling pin slots 812. If desired, thetemplate may be color coded to further assist test personnel inreprogramming the configuration of the carrier plate (for example, tomore easily distinguish between support holes and fixed tooling pinholes).

The above description of illustrated embodiments of the invention,including what is described in the Abstract, is not intended to beexhaustive or to limit the invention to the precise forms disclosed.While specific embodiments of, and examples for, the invention aredescribed herein for illustrative purposes, various equivalentmodifications are possible within the scope of the invention, as thoseskilled in the relevant art will recognize.

These modifications can be made to the invention in light of the abovedetailed description. The terms used in the following claims should notbe construed to limit the invention to the specific embodimentsdisclosed in the specification and the claims. Rather, the scope of theinvention is to be determined entirely by the following claims, whichare to be construed in accordance with established doctrines of claiminterpretation.

What is claimed is:
 1. An apparatus, comprising: a carrier plate havinga plurality of holes formed therein; and a plurality of alignmentcomponents, operatively coupleable to the carrier plate via saidplurality of holes, wherein the plurality of alignment components may berepositioned to facilitate alignment, relative to the carrier plate, ofcircuit boards having different form factors.
 2. The apparatus of claim1, wherein the plurality of holes are arrayed in a grid.
 3. Theapparatus of claim 1, wherein at least a portion of the plurality ofholes comprise threaded holes, and at least one of the plurality ofalignment components are operatively coupled to the carrier plate viathreaded fasteners threaded into corresponding threaded holes.
 4. Theapparatus of claim 1, further comprising a plurality of supports,operatively coupleable to the carrier plate via said plurality of holes,to support a circuit board so that it is not in contact with the carrierplate.
 5. The apparatus of claim 1, wherein the alignment componentsinclude at least one repositionable fixed tooling pin that isoperatively coupleable to the carrier plate via a respective hole. 6.The apparatus of claim 1, wherein the alignment components include atleast one adjustable tooling pin, operatively coupleable to the carrierplate via said plurality of holes, enabled to be adjusted in positionrelative to said plurality of holes.
 7. The apparatus of claim 6,wherein the adjustable tooling pin comprises a bar having a tooling pinextending upward thereform and having a slot for receiving a shank endof one or more fasteners that are used to secure the bar to the carrierplate.
 8. The apparatus of claim 1, wherein the plurality of alignmentcomponents include at least one alignment block.
 9. The apparatus ofclaim 1, wherein the carrier plate further comprises a handle coupledthereto.
 10. The apparatus of claim 1, wherein the carrier plate furthercomprises a location slot defined in an underside thereof to align thecarrier plate with a corresponding member of a test apparatus in whichthe carrier plate may be employed.
 11. The apparatus of claim 1, furthercomprising a pair of alignment bushings, disposed in respective holesdefined in the carrier plate, said alignment bushings adapted to receiverespective shafts comprising members in a test apparatus in which thecarrier plate may be employed.
 12. The apparatus of claim 1, furthercomprising an alignment template defining locations for the plurality ofalignment components.
 13. An apparatus comprising: reconfigurable meansfor supporting a circuit board; and reconfigurable means for aligningthe circuit board relative to a predetermined datum and orientation ofthe reconfigurable means for supporting the circuit board, wherein thereconfigurable means for supporting the circuit board and reconfigurablemeans for aligning the circuit board can be reconfigured to support andalign respective circuit boards having different form factors.
 14. Theapparatus of claim 13, further comprising means for grossly aligning thecircuit board relative to the predetermined datum and orientation. 15.The apparatus of claim 14, wherein the means for aligning the circuitboard relative to the predetermined datum and orientation includes apair of tooling pins.
 16. The apparatus of claim 15, wherein one of thetooling pins is adjustable.
 17. The apparatus of claim 13, wherein themeans for supporting the circuit board comprises a carrier plate,further comprising means for aligning the carrier plate with a testapparatus in which the carrier plate may be employed.
 18. The apparatusof claim 13, wherein the means for supporting the circuit board includesmeans for electrically isolating the circuit board.
 19. The apparatus ofclaim 13, wherein the means for supporting the circuit board comprises acarrier plate, further comprising means for aligning the carrier platerelative to a test apparatus member on which the carrier plate is torest.
 20. The apparatus of claim 13, wherein the means for aligning thecircuit board relative to a predetermined datum and orientation isreconfigurable.
 21. The apparatus of claim 13, wherein the means foraligning the circuit board relative to the predetermined datum andorientation includes a plurality of alignment components, furthercomprising means for locating said plurality of alignment components.22. A method for aligning circuit boards having different form factors,each circuit board comprising a device under test (DUT) in a testapparatus, the method comprising: configuring alignment components on acarrier plate to correspond to a first form factor for a first DUT;placing the first DUT on the carrier plate such that the first DUT isaligned relative to the carrier plate via the alignment components;removing the first DUT from the carrier plate; reconfiguring thealignment components on the carrier plate to correspond to a second formfactor for a second DUT; and placing the second DUT on the carrier platesuch that the second DUT is aligned relative to the carrier plate viathe alignment components.
 23. The method of claim 22, further comprisingemploying a form-factor template to configure the alignment components.24. The method of claim 22, wherein the alignment components include apair of tooling pins configured to be received by corresponding holesdefined in the DUT.
 25. The method of claim 22, wherein the alignmentcomponents include a plurality if alignment blocks.
 26. The method ofclaim 22, further comprising configuring a plurality of supports on thecarrier plate in accordance with a form factor for a DUT to electricallyisolate the DUT from the carrier plate.